Abstract We consider query answering on Description Logic (DL) ontologies with DBoxes, where a DBox is a set of assertions on individuals involving atomic concepts and roles called DBox predicates. The extension of a DBox predicate is exactly defifined in every interpretation by the contents of the DBox, i.e., a DBox faithfully represents a database whose table names are the DBox predicates and the tuples are the DBox assertions. Our goals are (i) to fifind out whether the answers to a given query are solely determined by the DBox predicates and, if so, (ii) to fifind a rewriting of the query in terms of them. The resulting query can then be effificiently evaluated using standard database technology. We have that (i) can be reduced to entailment checking and (ii) can be reduced to fifinding an interpolant. We present a procedure for computing interpolants in the DL ALC with general TBoxes. We extend the procedure with standard tableau optimisations, and we discuss abduction as a technique for amending ontologies to gain defifinability of queries of interest